The use of a clamping nut to secure a component onto a shaft is common practice in many engineering applications (see FIG. 1). The action of tightening the clamping nut onto the shaft to create a clamping force causes an extension of the shaft with the consequential generation of strain in the shaft.
In space-critical situations it is often necessary to use a short nut to secure a short component, such as a bearing hub, onto a shaft. In such a situation, the amount of extension required in the shaft to produce a given clamping force against the component will necessarily be very small (typically in the region of approximately 0.1 mm to 0.2 mm). This requires precise control of the angular rotation of the clamping nut during the tightening process in order to achieve this level of extension.
A consequence of this level of required shaft extension is that an error of only approximately 0.02 mm in the extension of the shaft can lead to variations in the clamping force of up to approximately 20%, which variation may be technically unacceptable.
One approach to making the tightening of the bolted joint less sensitive to variation in angular rotation of the clamping nut is to increase the overall length of the clamped component stack by, for example, inserting a spacer between the clamping nut and the clamped component. However this approach may not always be possible if the additional length cannot be accommodated in the space available.